Be sure to check out the 2 hours worth of video as well as the references!. The webinar introduces API calls and compares / contrasts them to a browser call / Web scraping. It also covers a ton about pluses & minuses between the two.

I use Fiddler to help monitor network traffic. Check out my videos on Fiddler for monitoring Network Traffic. They can really help understand what is being sent from the Apps / Website so you know what you need to replicate.